title: Induction and prevention of severe hyperammonemia in the spfash mouse model of ornithine transcarbamylase deficiency using shRNA and rAAV-mediated gene delivery.
abstract: Urea cycle defects presenting early in life with hyperammonemia remain difficult to treat and commonly necessitate liver transplantation. Gene therapy has the potential to prevent hyperammonemic episodes while awaiting liver transplantation, and possibly also to avert the need for transplantation altogether. Ornithine transcarbamylase (OTC) deficiency, the most prevalent urea cycle disorder, provides an ideal model for the development of liver-targeted gene therapy. While we and others have successfully cured the spf(ash) mouse model of OTC deficiency using adeno-associated virus (AAV) vectors, a major limitation of this model is the presence of residual OTC enzymatic activity which confers a mild phenotype without clinically significant hyperammonemia. To better model severe disease we devised a strategy involving AAV2/8-mediated delivery of a short hairpin RNA (shRNA) to specifically knockdown residual endogenous OTC messenger RNA (mRNA). This strategy proved highly successful with vector-treated mice developing severe hyperammonemia and associated neurological impairment. Using this system, we showed that the dose of an AAV rescue construct encoding the murine OTC (mOTC) cDNA required to prevent hyperammonemia is fivefold lower than that required to control orotic aciduria. This result is favorable for clinical translation as it indicates that the threshold for therapeutic benefit is likely to be lower than indicated by earlier studies.
authors.affiliation: Gene Therapy Research Unit, Children's Medical Research Institute and The Children's Hospital at Westmead, Wentworthville, New South Wales, Australia.
authors.forename: Sharon C
authors.initials: SC
authors.lastname: Cunningham
authors.forename: Cindy Y
authors.initials: CY
authors.lastname: Kok
authors.forename: Allison P
authors.initials: AP
authors.lastname: Dane
authors.forename: Kevin
authors.initials: K
authors.lastname: Carpenter
authors.forename: Eddy
authors.initials: E
authors.lastname: Kizana
authors.forename: Philip W
authors.initials: PW
authors.lastname: Kuchel
authors.forename: Ian E
authors.initials: IE
authors.lastname: Alexander
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D000229:Dependovirus / Q000235:genetics; D004195:Disease Models, Animal; D055785:Gene Knockdown Techniques; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D022124:Hyperammonemia / Q000235:genetics* / Q000628:therapy*; D008099:Liver / Q000473:pathology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009954:Ornithine Carbamoyltransferase / Q000235:genetics / Q000378:metabolism*; D020163:Ornithine Carbamoyltransferase Deficiency Disease / Q000235:genetics* / Q000628:therapy*; D009963:Orotic Acid / Q000032:analysis / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D020413:3' Untranslated Regions; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D009963:Orotic Acid; D009954:Ornithine Carbamoyltransferase